Inhalers are commonly used to administer medication such as bronchodilators, corticosteroids and anti-allergenics to the pulmonary tracts of humans and other animals, and in particular to treat nasal and bronchial complaints such as asthma.
A typical inhaler includes a canister, having a nozzle, containing the drug or medicine, and a detachable casing for attachment to the canister. In most applications, the canister contains the drug in powder or liquid form, and the dispensing action forces out a regulated dose of the drug in aerosol form.
The aerosol may be created using a propellant e.g. CFC or HFA forced through the drug by the dispensing motion, or more preferably in PMDIs (pressurised measured-does inhaler) by creation of a significant overpressure inside the canister.
In most PMDIs, the dispensing action consists of moving the canister relative to the casing, the action of the casing on the nozzle of the canister causing the predetermined dose to be released when the nozzle has been depressed a set distance.
Existing inhalers therefore include a detachable casing having a seat member that is engaged with the canister nozzle when the canister is removably inserted to the casing. In most existing inhalers the seat member includes a gripping portion for gripping the nozzle, so that the canister is held in the casting, but only held so that the canister can be easily withdrawn from the casing by simply pulling the canister and casing in opposite directions.
This is the problem that exists. Once the inhaler canister is detached from the housing and mixed with other canisters, for example, to wash the mouth piece out or clean the canister nozzles, there is no means of being able to determine the number of uses that particular canister has left, especially when it is mixed in with other canisters of the same type. It is common for users to have several canisters to ensure that they do not run out of the drug. Keeping count of which canister is still with drugs inside can be a problem.
Typical PMDI canisters for use in PMDIs contain between 60 and 200 doses, and may be used on a daily basis, or only occasionally to relieve particular symptoms. In most cases the patient is unlikely to keep a record of the number of doses administered, so will not be aware when the canister is near to being empty. The patient will not necessarily be immediately aware that the drug is no longer being dispensed when they use the canister as the pressure of the canister, or the dispensing motion, may not change. This could be a potentially serious problem for the patient, resulting in an emergency when they find that the drug in their inhaler had been exhausted by an earlier use. This can cause more anxiety and lead to more emotional distress.
Therefore, there is a need for some form of counting device which can count the number of doses dispensed from a canister to provide an indication of when the canister is empty. In order to be of use, such a counting device must accurately record each actuation of the canister.
Previous attempts to provide such a counting device have had a number of drawbacks. In particular, some solutions have been proposed with a counting device which is mounted on the casing of the inhaler and records each actuation of the canister using, for example, a pressure pad or a lever based switch. These devices suffer from the problem that they either have to be reset manually, or if a canister is removed from the inhaler, the counter automatically resets, so if the same canister is replaced (e.g. after cleaning), the reading will be incorrect.
To overcome this problem, there are many other solutions proposed to try and keep a count of the contents of the remaining drug. However most of these also still have the problem that the count of the drug remains with the housing rather than the canister thus making the design have the same problem that the user still does not know how much is left in the canister should they swap it for another.
These devices can use different techniques but most of them being too costly to manufacture or are too complex in function to allow them to function correctly when mass produced. While these patents are novel in the technique, non of them consider the impact in manufacturing a solution for the public to use the design sufficiently to provide a reasonably accurate indication of the remaining drug.
The design outlined in this patent is to show how an indicator can be designed for manufacture using the manufacturing experience of the Inventor as well as novel design techniques to provide a calibration free design that can be manufactured for the mass market and provide a form of indication to asthmatic users. It is documented that the University of Michigan in 1995 conducted a survey in which it is reported that 54% of asthmatic users do not know the amount of drug remaining in the canister while only 8% actually tracked the amount of usage. It is apparent that major reasons on the lack of designs in the market are precisely because of the cost and complexity of the designs to provide a manufacturability solution. For example the following patents are considered too complex for manufacture:—PCT WO92/17231 by INNOMED shows a set of contact rings on the canister and a set of sensors in the housing. There is no reference to how this would work in the field when you consider calibration, contact problems inside the housing, assembly and user friendly of removing and reinserting the canister. The count is still displayed on the housing rather than on the canister.
Patent US006148815A by James L Wolf shows very complex design built into the housing that will allow to do a number of functions of counting and interfacing to external devices. The one function it does NOT do is to allow the canister to keep the count on the canister so once removed from the housing there is no knowledge of what is left in the canister when reinserted to the housing. Again for manufacture assembly it is very complex and difficult making the unit costly and difficult to use.
EP 0684047 A3 by Walker, William shows a complex counting system attached to the side of the housing and using the vertical displacement of movement of the canister to count. Again housing contains the count while the canister once removed has no means of indication what amount of drug is remaining.
Patent US005411173A by Albert Weinstein shows a spray dispenser. This is similar to the Walker William version except it is upside down for use with an upright spray. The problem again is the complexity to achieve the count and again it does NOT hold the count on the canister when it is removed from the housing.
Patent US006202642B1 by Robert J McKinnon shows a very complex design in which the canister is complexly housed in the housing. Again once removed from the housing there is no count retained by the canister.
Assembly for manufacture is very complex and difficult to use.
Patent WO 02/36190 A2 by Glaxo Group ltd gives a design which incorporates feedback of the drug being released when the dispenser is used. This is accurate but complex to manufacture and calibrate for the user. Again the counter is NOT retained with the canister once removed from the housing.
Patent US005284133A by James S Burns gives a detailed design based on the counter on the housing. Again the count is not retained by the canister once removed from the housing.
The above list is just a few of the designs that have been invented. They all use the relative motion of the canister to the housing to dispense the drug and have numerous ways of indicating the usage. The problem with most of them is that they use the housing to hold the count information rather than the canister. Other patents such as WO 031/103759 A1 by Trumeter company ltd and WO 01/28887 by Glaxo Group Ltd has the indicator on the nozzle and has it assembled onto the front part of the canister. The relative movement of nozzle to this attachment is the method of count. This is an acceptable design but it is complex to manufacture.
All of the designs use power from a battery and do not necessarily disclose the replacement of it and some may be subject to being thrown away after use due to the battery expiring.